Exploratory Immunohistochemical Mapping of Mechanosensitivity-Associated Ion Channel Proteins in Terminal Glial Cells of Human Meissner and Pacinian Corpuscles

Terminal glial cells (TGCs) of cutaneous end-organ complexes have traditionally been regarded as structural and trophic elements, although they may also participate in mechanosensory processing. We performed an exploratory immunohistochemical and immunofluorescence study of mechanosensitivity-associated ion channel proteins in human Meissner and Pacinian corpuscles using archival formalin-fixed, paraffin-embedded glabrous skin from 64 donors and several anatomical sites. Immunoreactivity was assessed separately in mechanoreceptor axons and TGCs. In Meissner corpuscles, TGC-associated immunoreactivity for ASIC2 and TRPV4 was observed in subsets of evaluable corpuscles, whereas TRPA1 immunoreactivity was observed in selected specimens. PIEZO1- and PIEZO2-associated immunoreactivity was observed in subsets of corpuscles from the single available labia minora specimen. Among evaluable Pacinian corpuscles, inner-core TGC-associated immunoreactivity was observed for ASIC2, PIEZO2, TRPA1, and TRPV4. Because Pacinian corpuscles were unevenly distributed and scarce outside hand and foot skin, these findings were interpreted exclusively descriptively. To our knowledge, TRPA1 immunoreactivity has not previously been described in TGCs of human sensory corpuscles. These findings are hypothesis-generating and do not demonstrate protein function or mechanotransduction. Because this study used archival tissue and independent target validation was not performed, the results require confirmation using orthogonal antibody- or transcript-based approaches.